Field Of The Invention
[0001] This invention generally relates to a mixing apparatus and a method useful in the
manufacture of can ends used in the food and beverage packaging industries. More specifically,
the invention provides a mixing apparatus and a method for use in the corrosion preventative
repair of tooling induced damage to can end coatings, which may occur to coated steel
can ends during the conversion of a steel shell into a full open or easy open food
or beverage can end.
Background Of The Invention
[0002] Many can bodies for food, beverages or other products are provided with easy open
can ends that are characterized by having a pull tab attached to the can end which
is used to fracture a tear panel on the can end defined by a score line on the can
end. The pull tab may be lifted to depress the tear panel in order to provide an opening
in the can end for dispensing the contents of the container.
[0003] Likewise, many food products are sold in can bodies provided with full open easy
open can ends that are characterized by having a pull tab attached to the can end
which is used to fracture a score line that circumscribes the circumference of the
end panel to define an opening panel. The pull tab may be lifted to fracture the score
line. After the score line is fractured, the pull tab may be pulled upward from the
container which severs the remainder of the score line in order to remove the entire
opening panel for dispensing the contents of the container.
[0004] In the manufacture of an easy open can end, a shell is conveyed to a conversion press.
In the industry, a pre-converted can end is commonly referred to as a shell. In the
typical operation of a conversion press, a shell is introduced between an upper tool
member and a lower tool member, which are in the open, spaced apart position. A press
ram advances the upper tool member toward the lower tool member in order to perform
any of a variety of tooling operations such as rivet forming, paneling, scoring, embossing,
and final staking. After performing a tooling operation, the press ram retracts until
the upper tool member and lower tool member are once again in the open, spaced apart
position. The partially converted shell is transported to the next successive tooling
operation until an easy open can end is completely formed and discharged from the
press. As one shell leaves a given tooling operation, another shell is introduced
to the vacated operation, thus continuously repeating the entire easy open can end
manufacturing process. Examples of easy open can ends can be found in
U.S. Pat. Nos. 4,465,204 and
4,530,631. Conversion presses can operate at speeds that manufacture in,excess of 500 can ends
per minute per lane, with certain presses having four lanes of tooling manufacturing
in excess of 2000 converted can ends per minute.
[0005] It has been the practice in the industry to continue to strive to reduce the starting
gauge of the metal sheet stock used to form the can end. The current practice is to
use metal with a starting gauge of approximately 0.008 inch (0.20 mm). As such, tooling
stations in a conversion press must be rigorously maintained within prescribed operating
tolerances due to the thin sheet stock used in the press. In the production of a converted
can end in a conversion press, the scoring station is of particular concern. The scoring
station employs a tooling member that has a knife edge which defines the tear panel
or opening panel on the public side of the can end.
[0006] Steel sheet stock used in the manufacture of can ends has a coating which protects
the metal by inhibiting oxidation, corrosion or rust from forming on the surface of
the metal. During the conversion process, damage to the protective coating typically
occurs while forming the score that defines the tear panel or opening panel of the
can end. As noted above, in the conversion of a shell into a can end with openable
features thereon, a score line is formed. This score line defines the tear panel or
opening panel described above. The score line is the most likely location where damage
is caused to the pre-conversion, protective coating. Any oxidation, corrosion or rust
on the surface of the can end represents an unattractive product appearance to the
consumer and is unacceptable to canmakers in general.
[0007] In the industry, as a precautionary measure to prevent oxidation, corrosion or rust
from appearing on the can end, many canmakers apply a mixed solution to the scored
area of the can end by spraying the can end. The accepted spraying apparatus and method
in the industry for score repair on full open easy open ends utilizes a single holding
tank that holds a plurality of components (e.g., solvent and epoxy) that are flowed
through a fluid delivery system and a spray apparatus for applying the mixed solution
to the can end.
[0008] These score repair machines use many different variations of two or more component
epoxy mixtures for the application of mixed solution to the score lines of the can
end. The fluid delivery systems require routine maintenance because the two or more
component mixed solution has a finite tank life when mixed and need to be cleaned
or purged from the machine when the mixed solution expires. The existing fluid delivery
systems pump mixed solution and the mixed solution wets many of the pumping components
and auxiliary components including, by way of example and not limitation, filters,
valves, pumps, pressure transducers and check valves, etc. The mixed solution has
a negative effect on the overall efficiency of many components of the machine because
so many components are wetted with the mixed solution and require cleaning when the
mixed solution expires.
[0009] Conversely, the mixing apparatus and method of the present invention will mix the
components of the mixed solution on demand. The apparatus also contains a pressure
tank that eliminates the exposure of the mixed solution to the pumping components
and auxiliary components used in the fluid delivery system which simplifies cleaning
and maintenance of the fluid delivery system. The apparatus of the present invention
does not have any high pressure pumps or repair fluid pressure regulators that contact
the mixed solution and can be designed for low pressure spray devices or high pressure
spray devices. The apparatus also provides the end-user with greater flexibility by
being able to use different mixing ratios of the base components (e.g., 4:1 - solvent:epoxy,
or any other combination.) The apparatus also allows the holding tanks to be continuously
replenished with liquids or fluids while the mixing apparatus is operating because
the liquids or fluids are drawn from storage tanks at atmosphere.
[0010] There continues to be a need in the art for a mixing apparatus and method of the
present invention that mixes components of a mixed solution on demand. Also, there
continues to be a need in the art for a mixing apparatus and method of the present
invention that uses a pressure tank that eliminates the exposure of the mixed solution
to the pumping components and auxiliary components used in the system in order to
simplify cleaning and maintenance of the fluid delivery system. Additionally, there
continues to be a need in the art for a mixing apparatus and method of the present
invention that can accommodate different mixing ratios of the components of the mixed
solution. Also, there continues to be a need in the art for a mixing apparatus and
method of the present invention that allows holding tanks to be continuously replenished
with liquids or fluids while the mixing apparatus is operating.
Summary of the Invention
[0011] It is an object of the present invention to provide a mixing apparatus and method
that mixes repair fluid components on demand. It is an additional object of the present
invention to provide a mixing apparatus and method that uses a pressure tank that
eliminates the exposure of the mixed repair fluid solution to the pumping components
and auxiliary components used in the fluid delivery system in order to simplify cleaning
and maintenance of the fluid delivery system. It is an additional object of the present
invention to provide a mixing apparatus and method that can accommodate different
mixing ratios of the repair fluid components. It is an additional object of the present
invention to provide a mixing apparatus and method that allows holding tanks to be
continuously replenished with liquids or fluids while the mixing apparatus is operating.
[0012] According to a first aspect of the present invention, there is provided a mixing
apparatus for the repair of coating adhered on a can end, comprising:
a plurality of holding tanks in fluid communication with a first delivery system and
a mixer;
a pressure tank in fluid communication with the mixer; and
a spray device in fluid communication with a second fluid delivery system and the
pressure tank;
wherein a plurality of liquids or fluids are flowed through the first fluid delivery
system,
wherein the plurality of liquids or fluids are mixed in the mixer to yield a mixed
solution which is flowed to the pressure tank, and
wherein the mixed solution is flowed through the second fluid delivery system and
dispensed on the can end.
[0013] Preferably, the first fluid delivery system further comprises additional elements.
[0014] Advantageously, the additional elements are selected from the group consisting of
valves, conduits, hoses passageways, pumps, pressure transducers, pressure relief
valves and check valves.
[0015] Conveniently, the second delivery system further comprises additional elements.
[0016] Preferably, wherein the additional elements are selected from the group consisting
of conduits, hoses, passageways, filters and flow sensors.
[0017] Advantageously, a relieving type pressure regulator is coupled to the pressure tank.
[0018] Conveniently, a check valve separates the pressure tank and the mixer.
[0019] Preferably, a plurality of check valves separate the mixer from the first fluid delivery
system.
[0020] Advantageously, the first fluid delivery system has a plurality of valves coupled
to the holding tanks, wherein the valves selectively flow liquids or fluids held in
the holding tanks in the first fluid delivery system,
the first fluid delivery system having a plurality of pumps, wherein the pumps pump
the liquids or fluids to flow the liquids or fluids into the mixer;
a relieving type pressure regulator coupled to the pressure tank; and
wherein pressure in the pressure tank flows the mixed solution through the second
fluid delivery system and dispenses the mixed solution on the can end.
[0021] According to another aspect of the present invention, there is provided a method
for the repair of coating adhered on a can end, comprising:
flowing a plurality of liquids or fluids from a plurality of holding tanks into a
first fluid delivery system in fluid communication with the holding tanks and a mixer;
flowing the plurality of liquids or fluids into the mixer;
mixing the plurality of liquids or fluids to yield a mixed solution;
flowing the mixed solution into a pressure tank;
flowing the mixed solution from the pressure tank into a second fluid delivery system
in fluid communication with the pressure tank and a spray device; and
dispensing the mixed solution on the can end.
[0022] Preferably, the method further comprises applying pressure to the mixed solution
in the pressure tank.
[0023] Advantageously, the method further comprises applying pressure to the plurality of
liquids or fluids in the first delivery system to flow the liquids or fluids into
the mixer.
[0024] Conveniently, the method further comprises applying pressure to the plurality of
liquids or fluids in the first delivery system to flow the liquids or fluids into
the mixer.
[0025] Preferably, the method further comprises releasing the pressure in the pressure tank.
[0026] Certain advantages are obtained by providing a mixing apparatus for the repair of
coating adhered on a can end. The mixing apparatus has a plurality of holding tanks
in fluid communication with a first fluid delivery system and a mixer. The pressure
tank is provided which is in fluid communication with the mixer. A spray device is
provided which is in fluid communication with a second fluid delivery system and the
pressure tank. A plurality of liquids of fluids are flowed through the first fluid
delivery system, the plurality of liquids or fluids are mixed in the mixer to yield
a mixed solution which is flowed to the pressure tank and the mixed solution is flowed
through the second fluid delivery system and dispensed on the can end.
[0027] Other advantages are obtained by providing a mixing apparatus for the repair of coating
adhered on a can end. The mixing apparatus has a plurality of holding tanks in fluid
communication with a first fluid delivery system and a mixer. The first fluid delivery
system has a plurality of valves coupled to the holding tanks, wherein the valves
selectively flow liquids or fluids held in the holding tanks into the first fluid
delivery system. The first fluid delivery system also has a plurality of pumps, wherein
the pumps pump the liquids or fluids to flow the liquids or fluids into the mixer.
A pressure tank is in fluid communication with the mixer and a relieving type pressure
regulator is coupled to the pressure tank. A spray device is in fluid communication
with a second fluid delivery system and the pressure tank, wherein the plurality of
liquids or fluids are mixed in the mixer to yield a mixed solution which is flowed
into the pressure tank. Pressure in the pressure tank flows the mixed solution through
the second fluid delivery system and dispenses the mixed solution on the can end.
[0028] Other advantages are obtained by providing a method for the repair of coating adhered
on a can end. The method comprises: flowing a plurality of liquids or fluids from
a plurality of holding tanks into a first fluid delivery system in fluid communication
with the holding tanks and a mixer; flowing the plurality of liquids of fluids into
the mixer; mixing the plurality of liquids or fluids to yield a mixed solution; flowing
the mixed solution into a pressure tank; flowing the mixed solution from the pressure
tank into a second fluid delivery system in fluid communication with the pressure
tank and a spray device; and dispensing the mixed solution on the can end.
Brief Description of the Drawings
[0029] So that the invention may be more readily understood, and so that further features
thereof may be appreciated, an embodiment of the invention will now be described,
by way of example, with reference to the accompanying drawings, in which :
FIG. 1 is a top plan view of a full open easy opening end; and
FIG. 2 is a schematic drawing of a mixing apparatus and a method for the repair of
can ends.
Detailed Description of the Preferred Embodiments
[0030] For purposes of the description hereinafter, the terms "upper", "lower", "vertical",
"horizontal", "top", "bottom", "aft", "behind", "forward", "rear", "beneath", "below",
and derivatives thereof shall relate to the invention, as it is oriented in the drawing
FIGS. However, it is to be understood that the invention may assume various alternative
configurations except where expressly specified to the contrary. It is also to be
understood that the specific elements illustrated in the drawings and described in
the following specification are simply exemplary embodiments of the invention. Therefore,
specific dimensions, orientations and other physical characteristics related to the
embodiments disclosed herein are not to be considered limiting.
[0031] As employed herein, the term "number" refers to one or more than one (
i.e., a plurality). As employed herein, the term "fastener" refers to any suitable fastening,
connecting or tightening mechanism expressly including, but not limited to, integral
rivets. As employed herein, the statement that two or more parts are "coupled", "attached"
or "connected" together shall mean that the parts are joined together either directly
or joined through one ore more intermediate parts.
[0032] Turning to FIG. 1, a full open easy open can end 10 is displayed. The can end 10
has a score line 12 which defines an opening panel 14. A pull tab 15 may be lifted
to fracture the score line 12. After the score line 12 is fractured, the pull tab
15 may be pulled upward from the container which severs the remainder of the score
line 12 in order to remove the entire opening panel 14 for dispensing the contents
of the container.
[0033] Turning to FIG. 2, a schematic drawing of a mixing apparatus 18 and a method for
the repair of can ends is shown. The mixing apparatus 18 has a plurality of holding
tanks 20 for holding various liquids or components of such liquids including, by way
of example and not limitation, liquid components of a repair fluid, lacquer, epoxy
or paint that when mixed together yield a mixed solution. Alternatively, one of the
holding tanks 20 could hold a liquid or solvent 22 for cleaning or flushing a first
fluid delivery system 24 which is in fluid communication with the holding tanks 20
and a mixer 40. The liquids dispensed from the holding tanks 20 could be, by way of
example and not limitation, any aqueous or organic liquid or fluid known in the art
which is suitable for: (i) mixing with one or more components to yield a mixed solution;
or (ii) dissolving or releasing liquids or fluids disposed within the first fluid
delivery system 24. The holding tanks 20 may be continuously replenished with liquids
or fluids while the mixing apparatus 18 is operating because the liquids or fluids
are drawn from storage tanks at atmosphere.
[0034] The holding tanks 20 and the first fluid delivery system 24 may have filters or strainers
26 that remove contaminants from the liquids or fluids flowed into the holding tanks
20 or the first fluid delivery system 24. The first fluid delivery system 24 of the
present invention may contain additional elements, by way of example and not limitation,
a plurality of first valves 28, a plurality of second valves 30, a plurality of conduits,
hoses or passageways 32, a plurality of pumps 34, a plurality of pressure transducers
36, a plurality of pressure relief valves 38 or a plurality of second check valves
50. The plurality of first valves 28 are coupled to the holding tanks 20 for selectively
flowing the contents of one or more of the holding tanks 20 through the first fluid
delivery system 24 by a programmable logic control device or other control device.
The plurality of second valves 30 are coupled to the first valves 28 for selectively
flowing the contents of one or more of the holding tanks 20 through the first fluid
delivery system 24 by a programmable logic control device or other control device.
The first fluid delivery system 24 may contain a plurality of conduits, hoses or passageways
32 for flowing the liquids or fluids held in the holding tanks 20 which are in fluid
communication with the conduits, hoses or passageways 32. The conduits, hoses or passageways
32 are in fluid communication with the mixer 40. The first fluid delivery system 24
may also contain a plurality of pumps 34 coupled to the plurality of pressure transducers
36. The pumps 34 are metering pumps with an eccentric drive element for selectively
applying pressure and pumping the liquids or fluids that were held in the holding
tanks 20 to flow such liquids or fluids into the mixer 40 and on into a small pressure
tank 42. The pressure transducers 36 coupled to the pumps 34 are used to selectively
monitor the pressure in the first fluid delivery system 24 to ensure flow within the
first fluid delivery system 24 between a selected value lower than the operating pressure
of the mixing apparatus 18 and the limiting upper end of pressure allowed for pumps
34 by a programmable logic control device or other control device. The first fluid
delivery system 24 may also contain a plurality of pressure relief valves 38 which
check the first fluid delivery system 24 for blockage or obstruction downstream from
the pumps 34 by a programmable logic control device or other control device. These
pressure relief valves 38 are designed to mechanically relieve pressure at a value
that is less than the maximum operating pressure of the pumps 34 selected. The pressure
relief valves 38 protect the pumps 34 from pressure surges due to blockages or obstruction
downstream while the pressure transducers 36 are shutting off motor motion to the
pumps 34.
[0035] The liquids or fluids held in the holding tanks 20 flow under pressure supplied by
pumps 34 through the first fluid delivery system 24 into the mixer 40 which mixes
the liquids or fluids to yield a small amount of a mixed solution prior to flowing
the mixed solution from the pressure supplied by pumps 34 into the small pressure
tank 42 which is in fluid communication with mixer 40. The pressure tank 42 has a
size of about 1 gallon (3.79 liters) whereas existing fluid delivery systems that
pump mixed solution through the pumping components and the auxiliary components have
a pressure tank size of about 15 gallons (56.78 liters). As can be seen, the size
of the pressure tank 42 of the present invention is a substantial reduction over the
size of the pressure tank in existing fluid delivery systems that pump mixed solutions.
It has been found that the 1 gallon (3.79 liters) size also meets the maximum flow
demands observed in operation of the mixing apparatus 18. Generally speaking, about
1 gallon (3.79 liters) per hour is about the maximum mixed solution output that has
been observed, which allows for a smaller volume of mixed solution to be stored in
pressure tank 42. Such an approach also avoids running pumps 34 continuously to pump
the liquids or fluids from holding tanks 20 into the pressure tank 42 leading to an
energy savings in the operation of the present invention. A supply of gas optionally
flows into an amplifier 44 which increases the pressure of the gas. A pressure regulator
46 may be coupled to the optional amplifier 44 and coupled to the pressure tank 42
for selectively relieving the pressure of the gas in the pressure tank 42. The amplifier
44 is typically provided in those systems that use a high pressure droplet or atomization
spray method on a spray device 58. The amplifier 44 is typically not provided in those
systems that use a low pressure solid stream or non-atomization spray method on the
spray device 58.
[0036] The small pressure tank 42 eliminates the exposure of the mixed solution to the pumping
components and the auxiliary components located within the first fluid delivery system
24 such as first valves 28, second valves 30, conduits, hoses or passageways 32, pumps
34, pressure transducers 36, pressure relief valves 38 and second check valves 50
and allows small amounts of liquids or fluids held in holding tanks 20 to be selectively
mixed at the discretion of the end-user. As previously mentioned, prior art mixing
systems require routine cleaning and maintenance because the mixed solution has a
finite life span and requires more frequent cleaning of the pumping components and
the auxiliary components such as first valves 28, second valves 30, conduits, hoses
or passageways 32, pumps 34, pressure transducers 36, pressure relief valves 38 and
second check valves 50 that may come in contact with the mixed solution. The present
invention which does not have mixed solution contacting such elements reduces the
amount of cleaning and maintenance that is needed for the first fluid delivery system
24. As such, the first fluid delivery system 24 may be easily cleaned with any aqueous
or organic liquid or fluid known in the art which is suitable for dissolving or releasing
liquids or fluids disposed within the first fluid delivery system 24.
[0037] The mixer 40 is coupled to a first check valve 48 which separates the contents of
the pressure tank 42 and the mixer 40. The mixer 40 is also coupled to a plurality
of second check valves 50 which separate the mixer 40 from the first fluid delivery
system 24. With the present invention, after the liquids or fluids have been mixed,
the mixed solution is flowed from pressure tank 42 through a second fluid delivery
system 52 which may contain additional elements, including, by way of example and
not limitation, conduits, hoses, passageways, one or more filters 54 or one or more
flow sensors 56. Spray devices 58 are coupled to pressure tank 42, filters 54, flow
sensors 56 and are in fluid communication with the second fluid delivery system 52
and the pressure tank 42. The small size of the pressure tank 42 and the small amount
of mixed solution stored therein allows the second fluid delivery system 52 to be
easily cleaned with any aqueous or organic liquid or fluid known in the art which
is suitable for dissolving or releasing mixed solution disposed within the second
fluid delivery system 52.
[0038] The pressure generated by the pumps 34 provide enough pressure to the liquids or
fluids in the first fluid delivery system 24 to overcome the pressure in the pressure
tank 42 where a small amount of the mixed solution is stored. The relieving type pressure
regulator 46 coupled to the pressure tank 42 selectively controls the pressure that
flows the mixed solution from the pressure tank 42 through the second fluid delivery
system 52. The pressure regulator 46 is a relieving type to allow for relieving pressure
due to the changing volume of mixed solution in the pressure tank 42 as well as to
relieve the higher pressure generated by pumps 34 to flow the liquids or fluids held
in the holding tanks 20 into the pressure tank 42. The filters 54 remove contaminants
from the mixed solution flowed from the pressure tank 42 through the second fluid
delivery system 52. The mixed solution then flows through fluid flow sensors 56 which
monitor the flow rate of the mixed solution. The fluid flow sensors 56 allow the end-user
to selectively monitor the flow rate of the mixed solution from the spray devices
58. By monitoring the flow rate of the mixed solution from the spray devices 58, the
end-user can identify changes in the amount or weight of mixed solution that is dispensed
onto each can end 10 (e.g., blockages, line failures, etc.). The mixed solution then
flows to the rotating or translating spray devices 58 attached to a spray machine
which are rotating or translating in a circular or elliptical pattern and dispensing
mixed solution on the can ends 10.
[0039] While specific embodiments of the invention have been described in detail, it will
be appreciated by those skilled in the art that various modifications and alternatives
to those details could be developed in light of the overall teachings of the disclosure.
Accordingly, the particular arrangements disclosed are meant to be illustrative only
and not limiting as to the scope of the invention which is to be given the full breadth
of the claims appended hereto and any and all equivalents thereto.
[0040] When used in this specification and claims, the terms "comprises" and "comprising"
and variations thereof mean that the specified features, steps or integers are included.
The terms are not to be interpreted to exclude the presence of other features, steps
or components.
[0041] The features disclosed in the foregoing description, or the following claims, or
the accompanying drawings, expressed in their specific forms or in terms of a means
for performing the disclosed function, or a method or process for attaining the disclosed
result, as appropriate, may, separately, or in any combination of such features, be
utilised for realising the invention in diverse forms thereof.
1. A mixing apparatus for the repair of coating adhered on a can end, comprising:
A plurality of holding tanks in fluid communication with a first delivery system and
a mixer;
a pressure tank in fluid communication with the mixer; and
a spray device in fluid communication with a second fluid delivery system and the
pressure tank;
wherein a plurality of liquids or fluids are flowed through the first fluid delivery
system,
wherein the plurality of liquids or fluids are mixed in the mixer to yield a mixed
solution which is flowed to the pressure tank, and
wherein the mixed solution is flowed through the second fluid delivery system and
dispensed on the can end.
2. The mixing apparatus of claim 1, wherein the first fluid delivery system further comprises
additional elements.
3. The mixing apparatus of claim 2, wherein the additional elements are selected from
the group consisting of valves, conduits, hoses passageways, pumps, pressure transducers,
pressure relief valves and check valves.
4. The mixing apparatus of any preceding claim, wherein the second delivery system further
comprises additional elements.
5. The mixing apparatus of claim 4, wherein the additional elements are selected from
the group consisting of conduits, hoses, passageways, filters and flow sensors.
6. The mixing apparatus of any preceding claim, wherein a relieving type pressure regulator
is coupled to the pressure tank.
7. The mixing apparatus of any preceding claim, wherein a check valve separates the pressure
tank and the mixer.
8. The mixing apparatus of any preceding claim, wherein a plurality of check valves separate
the mixer from the first fluid delivery system.
9. A mixing apparatus according to any preceding claim, wherein
the first fluid delivery system has a plurality of valves coupled to the holding tanks,
wherein the valves selectively flow liquids or fluids held in the holding tanks in
the first fluid delivery system,
the first fluid delivery system having a plurality of pumps, wherein the pumps pump
the liquids or fluids to flow the liquids or fluids into the mixer;
a relieving type pressure regulator coupled to the pressure tank; and
wherein pressure in the pressure tank flows the mixed solution through the second
fluid delivery system and dispenses the mixed solution on the can end.
10. A method for the repair of coating adhered on a can end, comprising:
flowing a plurality of liquids or fluids from a plurality of holding tanks into a
first fluid delivery system in fluid communication with the holding tanks and a mixer;
flowing the plurality of liquids or fluids into the mixer;
mixing the plurality of liquids or fluids to yield a mixed solution;
flowing the mixed solution into a pressure tank;
flowing the mixed solution from the pressure tank into a second fluid delivery system
in fluid communication with the pressure tank and a spray device; and
dispensing the mixed solution on the can end.
11. The method of claim 10, further comprising applying pressure to the mixed solution
in the pressure tank.
12. The method of claim 10 or claim 11, further comprising applying pressure to the plurality
of liquids or fluids in the first delivery system to flow the liquids or fluids into
the mixer.
13. The method of any one of claims 10 to 12, further comprising checking the pressure
in the first fluid delivery system for obstruction.
14. The method of any one of claims 10 to 13, further comprising releasing the pressure
in the pressure tank.